The aim of this study was to evaluate the validity and reliability of an integrated assessment of competence using the Total Client Care (TCC) assessment tool within an undergraduate Nursing programme. The Total Client Care Assessment Tool aims to assess multiple competencies in an integrated way thereby mirroring the way in which registered nurses are expected to practice. TCC is a tool designed to assess the student's ability to provide holistic care to a client over a specified period of time. TCC measures the student's performance around four constructs, these are: Communication, Planning and Responding, Care Delivery and Assessing and Evaluating. G-theory analysis revealed satisfactory levels of global reliability on single use G co-efficient 0.90 although this dropped to 0.76 when used on eight occasions to assess the same students over a two year period. Analysis of variance revealed that students and assessment occasions accounted for most of the variance. The TCC assessment tool is useful as it provides data about the student's performance when providing actual care. When used as part of a wider system of assessment involving triangulation of evidence from a number of sources the tool can support mentor judgements about the achievement of competence.